Below-Grade Detail

Instead of lowering the new mudroom floor to match the elevation of the old entry into the garage, as called for by the plans, we took advantage of an extension to the garage roof to create headroom above the old garage.

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Figure 3. Instead of lowering the new mudroom floor to match the elevation of the old entry into the garage, as called for by the plans (left), the author took advantage of an extension to the garage roof (above) to create headroom above the old garage. This allowed him to raise the entryway and keep the mudroom floor at the same level.

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The added headroom allowed us to raise the entryway and keep the mudroom floor at the same level.

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Figure 4. Before opening up the houses rear wall, the crew bolted a pair of 134-inch by 18-inch LVLs through the exterior sheathing and into the second-story floor framing to support the shed roof of the addition and the second-story framing of the main house (A). Once the house wall was removed (B), they added ceiling joists flush with the existing ones on the other side of the beam. To open up the new eating area, they also replaced an old dropped header with a new flitch beam, first cutting back the joist ends, then slipping it into place (C, D). The two new headers intersect near a support post (E), as indicated in the drawing (facing page).

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Rob Corbo

Before opening up the house’s rear wall, the crew bolted a pair of 1-3/4-inch by 18-inch LVLs through the exterior sheathing and into the second-story floor framing to support the shed roof of the addition and the second-story framing of the main house.

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Once the house wall was removed, they added ceiling joists flush with the existing ones on the other side of the beam.

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To open up the new eating area, they also replaced an old dropped header with a new flitch beam, first cutting back the joist ends. . . .

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. . . then slipping it into place.

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The two new headers intersect near a support post.

When the homeowners bought the property, they inherited an ugly railroad-tie retaining wall that prevented the ground from coming into contact with the home’s cedar siding at one corner of the house (see slideshow). To eliminate it, I suggested that we regrade the backyard, but the architect explained that this option had already been rejected because of cost. Instead, he provided us with a below-grade detail that called for the removal of the retaining wall, a little excavation, and replacement of the original sheathing about 2 feet above the sill with treated plywood sheathing.

This was a detail that was inadvertently left off the bid plans; in hindsight, I should have ignored it at the start of the project and brought it up as an add-on later. But we were eager to land the job and build a relationship with this architect, so I agreed to include the work for $1,000, even though my estimate was closer to $3,000 (the work actually cost $3,300 to complete).

Before installing the PT plywood, we covered the exposed part of the foundation and mudsill with a generous coating of cold asphalt. We fastened the portion of the PT sheathing that fell below the sill to the foundation wall with powder-actuated fasteners. The asphalt layer helps seal the sheathing to the foundation and keeps moisture from wicking up the wall.

Next we installed 30-pound felt paper and galvanized wire lath over the plywood and parged the wall with a 1/2-inch-thick layer of mortar. Though parging isn’t completely waterproof, it will block most moisture from penetrating to the sheathing and old foundation wall underneath. We parged our new block work, too, so that the entire foundation would have a uniform appearance.

Finally, we coated the below-grade portion of the parged wall with more cold asphalt before laying in filter fabric and drainpipe and backfilling the trench with coarse stone. Then we folded the filter fabric back over the stone and leveled out the grade.

If the decision had been left up to me, I would have insisted that the yard be regraded; we never want to bring the ground into contact with anything other than solid masonry. But this detail was an uneasy compromise with the architect and client that kept the job on track, and we did the best we could to protect the framed wall from moisture and give it the appearance of a proper foundation. The foundation is well-drained, and since this part of the basement is unfinished, the wood foundation wall can be inspected easily from the inside for signs of moisture damage. Two years after project completion, the homeowners haven’t reported any problems.

Framing

During a previous renovation, the kitchen floor had been tiled and a tapered transition installed between the kitchen and family-room floors to deal with the out-of-level floor joists. While we couldn’t completely correct the old floor system, we spent a lot of time shimming and trimming the old joists as needed to smooth out the transition between the old and new spaces. Where the old floor was framed with 2x8s, we beefed it up with sistered 2x10s.

Originally, the architect’s plans called for a new mudroom and powder room adjacent to the garage to be two full steps below the kitchen floor, a design dictated by the elevation of an existing exterior garage door. However, the homeowners wanted all of the rooms to be on the same level, and we preferred to build the addition foundation so that the entire floor system would be level and as close to grade as possible. Fortunately, the roof design of the new addition allowed us to open up the garage ceiling and create enough headroom to raise the doorway between the mudroom and garage. Instead of putting a pair of steps between the mudroom and kitchen, we were able to add them to the set of stairs in the garage (see slideshow).

Exterior header. A 12-foot section of existing exterior wall had to be removed to connect the addition to the house. Even though the second-story floor joists ran parallel to the wall (and therefore were not supported by it), this wall still carried loads from the roof above.

We bolted two 1-3/4-inch by 18-inch LVLs through the sheathing and into the studs and the inside rim joist before demolishing the wall (see slideshow). At one end, this new flush header bears on another conventional LVL header that we installed for a new bay window. At the other end, it hangs from a new flush flitch-plate header.

Center wall header. During the remodel that had produced the out-of-level floor, a drop flitch-plate header had been installed to replace what had once been an exterior wall. To create a wider opening and a flush ceiling throughout the expanded kitchen, we replaced it with a longer flush flitch-plate header consisting of two 1-3/4-inch by 9-1/2-inch LVLs bolted around a 1/2-inch by 9-inch steel plate.